Liquid-crystal display device and method of driving the same

ABSTRACT

A liquid-crystal display device includes a liquid-crystal display panel having plural scanning electrodes in the form of lines and plural signal electrodes in the form of lines, a scanning signal generation section for supplying a scanning signal to each of the scanning electrodes, a data signal supply section for supplying a data signal to each of the signal electrodes, and a signal selection section. The signal selection circuit selectively controls each of the scanning electrodes so as to be capable of producing a display or so as to be incapable of producing a display. The scanning signal generation section, which is capable of generating h (h is an integer of 2 or more) types of scanning signals, supplies a scanning signal to each of the h scanning electrodes capable of producing a display at the same time in one period, and supplies the scanning signal to each of the other h scanning electrodes capable of producing a display at the same time in another period.

TECHNICAL FIELD

The present invention relates to a liquid-crystal display device whichis suitably used particularly in a method of selecting plural scanningelectrodes in the form of lines at the same time and driving them, andto a method of driving the same.

BACKGROUND ART

Generally, since liquid-crystal display devices have features, such assmall size and low profile, low power consumption, and flat-paneldisplay, they are widely used in display portions of wristwatches,portable game machines, notebook-type personal computers, liquid-crystaltelevisions, car navigation devices, and other electronic devices.

As methods of driving a liquid-crystal display panel, there are adriving method of selecting scanning electrodes one at a time anddriving them, and an MLS (multi-line selection) driving method (refer toInternational Application Publication No. WO93/18501) in which allscanning electrodes are grouped in advance and a scanning signal issimultaneously output to plural adjacent scanning electrodes belongingto the same group in a predetermined period. The MLS driving method hasan advantage in that power consumption can be reduced.

An example of a conventional liquid-crystal display device using an MLSdriving method will now be described with reference to FIGS. 11 to 13.As shown in FIG. 11, a conventional liquid-crystal display device 100has a liquid-crystal display panel 101. As shown in FIG. 12, theliquid-crystal display panel 101 has a substrate having plural scanningelectrodes (common electrodes) Y (Y1, Y2, . . . Ym) in the form oflines, a substrate having plural signal electrodes (segment electrodes)X (X1, X2, . . . Xn) in the form of lines, and a liquid-crystal layer(not shown) interposed between the two substrates. In order to drive theliquid-crystal display panel 101, a liquid-crystal driving circuit 102supplies, to each scanning electrode Y, a scanning signal which candiffer according to each scanning electrode and supplies, to each signalelectrode X, a data signal which can differ according to each signalelectrode. A liquid-crystal driving voltage generation circuit 103,which is connected to an input end of the liquid-crystal driving circuit102, generates a liquid-crystal driving voltage. A driving controlcircuit 104 is connected to the input ends of the liquid-crystal drivingcircuit 102 and the liquid-crystal driving voltage generation circuit103. When the driving control circuit 104 receives display data andcontrol data, the driving control circuit 104 generates a display signaland supplies it to the liquid-crystal driving circuit 102 and theliquid-crystal driving voltage generation circuit 103.

The liquid-crystal driving circuit 102 comprises a driving circuit 105on the scanning side which generates a scanning signal which is outputto a scanning electrode Y of the liquid-crystal display panel 101 and adriving circuit 106 on the signal side which generates a data signalwhich is output to a signal electrode X thereof when the liquid-crystaldriving voltage and the display signal are received.

Next, the driving operation of the liquid-crystal display device 100 isdescribed with reference to FIGS. 12 and 13. In this technique, thescanning electrodes Y are grouped in advance so that plural (3 in theexample of the figures) adjacent scanning electrodes belong to the samegroup. The driving circuit 105 on the scanning side drives threescanning electrodes Y belonging to the same group at the same time. Thatis, the driving circuit 105 on the scanning side generates a scanningsignal corresponding to each of the three scanning electrodes Y in apredetermined horizontal scanning period T. Then, another group isdriven at the same time, and the process proceeds to the driving ofanother group in sequence. On the other hand, the driving circuit 106 onthe signal side generates a data signal corresponding to each one of thesignal electrodes X1, X2, . . . Xn.

Specifically, as shown in part (a) of FIG. 13, the three scanningelectrodes Y1, Y2, and Y3 of the first group are selected in the firsthorizontal scanning period T, scanning signals are applied to thesescanning electrodes Y1, Y2, and Y3, and at the same time, data signalsare applied to the signal electrodes X. As shown in FIG. 13, thescanning signal and the data signal can change in an interval of aselection period Δt even within the same horizontal scanning period T.In the next horizontal scanning period T, as shown in part (b) of FIG.13, the scanning electrodes Y4, Y5, and Y6 of the next group areselected, and scanning signals having a waveform similar to thatsupplied to the scanning electrodes Y1, Y2, and Y3 are applied to thoseelectrodes. The application of the data signals to the signal electrodesX is performed continuously from the previous horizontal scanning periodT, and the waveform is different from the previous one. In this manner,the process proceeds to the driving of the next group, and when thedriving of the final group is terminated, the process returns to thedriving of the first group. The period of time required for the drivingof all the scanning electrode groups to be completed once, that is, theperiod of time required to scan one display area of the liquid-crystaldisplay panel 101 once, is called “one frame” (as indicated by F in FIG.13).

Since the voltage level of the scanning signal exists at two levels, +V2and −V2, if the number of scanning electrodes Y belonging to one group(the number of scanning electrodes which are selected at one time) isdenoted as h, the number of pulse patterns which can be realized by onegroup in one selection period Δt is 2^(h). That is, for example, asshown in FIG. 13, in a case where three scanning electrodes Y areselected at the same time, the number of pulse patterns which can berealized by one group in one selection period Δt is 2³=8. In the firstselection period Δt in the first horizontal scanning period T, thescanning electrode Y1 is off (voltage=−V2), the scanning electrode Y2 isoff, and the scanning electrode Y3 is off. In the next selection periodΔt, the scanning electrode Y1 is off, the scanning electrode Y2 is off,and the scanning electrode Y3 is on (voltage=+V2), and in sequence, adifferent pulse pattern is used in each selection period Δt.

The data signal applied to each signal electrode X is determined by theon/off of each of the pixels (3 pixels in the case of 3-linesimultaneous driving) which are objects for display at the same time onthat signal electrode, and the voltage level of the scanning signalapplied to the scanning electrode Y. For example, in this conventionaltechnique, during the period in which the voltage of a pulse of ascanning signal applied to the scanning electrodes Y1, Y2, and Y3 whichare selected at the same time is positive, the pixel display is assumedto be on; during the period in which the voltage of the pulse isnegative, the pixel display is assumed to be off; and the on/off of thedisplay data is compared with the voltage level of the scanning signalat each selection period Δt, so that the data signal is set according tothe number of mismatches.

Specifically, in the waveforms of the scanning signals sent to thescanning electrodes Y1, Y2, and Y3 in part (a) of FIG. 13, during theperiod in which a voltage of +V2 is applied, the pixel display isassumed to be on; during the period in which a voltage of −V2 isapplied, the pixel display is assumed to be off; a pixel in FIG. 12whose display is indicated as a black circle mark is assumed to be on,and a pixel whose display is indicated as a white circle mark is assumedto be off. The displays of the pixels at which the signal electrode X1intersects the scanning electrodes Y1, Y2, and Y3 in FIG. 12 are on, on,and off, in that order. It is assumed that data signals for obtainingsuch pixel displays are supplied. In contrast, the voltages applied tothe scanning electrodes Y1, Y2, and Y3 in the first selection period Δtindicate off, off, and off, respectively. Then, when both of thevoltages of the display data and of the scanning signals are comparedwith each other in sequence, the number of mismatches is 2. Therefore,in the first selection period Δt, a voltage V1 is applied to the signalelectrode X1, as shown in part (c) of FIG. 13. In the technique shown inFIG. 13, when the number of mismatches is 0, a pulse voltage of −V2 isapplied to the signal electrode X; when the number of mismatches is 1, apulse voltage of −V1 is applied thereto; when the number of mismatchesis 2, a pulse voltage of V1 is applied thereto; and when the number ofmismatches is 3, a pulse voltage of V2 is applied thereto. The voltageratio of V1 and V2 is set so as to satisfy V1:V2=1:2.

In the next selection period Δt, the voltages applied to the scanningelectrodes Y1, Y2, and Y3 indicate off, off, and on, respectively. Whenthese are compared with the on, on, and off displays of the pixels insequence, all the voltage levels of the scanning signals do not match,and the number of mismatches is 3. Therefore, a pulse voltage V2 isapplied to the signal electrode X1 in this selection period Δt. In asimilar manner, in the third selection period Δt, V1 is applied to thesignal electrode X1 at the third selection period Δt, and −V1 is appliedthereto in the fourth selection period Δt. Hereafter, voltages areapplied in the sequence of −V2, +V1, −V1, and −V1.

Furthermore, in the next horizontal scanning period T, the scanningelectrodes Y4 to Y6 of the next group are selected. When voltages havingwaveforms shown in part (b) of FIG. 13 are added to these scanningelectrodes Y4 to Y6, a data signal of a voltage level corresponding tothe mismatch between the on/off display of the pixels at which thescanning electrodes Y4 to Y6 intersect the signal electrodes and theon/off of the voltage levels of the scanning signals applied to thescanning electrodes Y4 to Y6 is applied to the signal electrode X1, asshown in part (c) of FIG. 13. Part (d) of FIG. 13 shows a waveformindicating a voltage applied to the pixel at which the scanningelectrode Y1 intersects the signal electrode X1, that is, a combinedwaveform of the scanning signal applied to the scanning electrode Y1 andthe data signal applied to the signal electrode X1.

As described above, in the MLS driving method for selecting pluralscanning electrodes at the same time in sequence and driving them,satisfactory contrast can be obtained, and furthermore, the drivingvoltage can be reduced.

In the liquid-crystal display device 100 using the MLS driving methodaccording to the above-described conventional art, the on/off of displaypixels is controlled by a combination of waveforms of a scanning signalsupplied to the scanning electrode Y and a data signal supplied to thesignal electrode X. For this reason, since it is necessary to setwaveforms to be supplied to both of the electrodes in advance, it isdifficult to diversify display modes irrespective of how the scanningelectrodes are grouped.

For example, regarding the size of font to be used, in the case of3-line MLS for selecting three scanning electrodes at the same time,grouping into a multiple of 3, such as 3 pixels, 6 pixels, or 9 pixels,in the vertical direction is easy. However, selection of other numbersof pixels causes signal control to be complex.

Furthermore, partial driving in which the screen of the liquid-crystaldisplay panel 101 is divided into display areas and non-display areas isoften performed to reduce power consumption. Here, in the conventionalMLS driving method, since plural scanning electrodes belonging to thesame group are always driven simultaneously, the width of the displayarea is completely limited by grouping. For example, if three scanningelectrodes are driven at the same time, the display area can have only awidth corresponding to lines of a multiple of 3. This applies similarlyto multi-row display, in which plural display areas are provided, inpartial driving.

DISCLOSURE OF THE INVENTION

The present invention provides a liquid-crystal display device employingan MLS driving method capable of realizing various displays, and amethod of driving the same.

According to one aspect of the present invention, the liquid-crystaldisplay device comprises:

a liquid-crystal display panel having a substrate having plural scanningelectrodes in the form of lines, a substrate having plural signalelectrodes in the form of lines, and a liquid-crystal layer interposedbetween the substrates;

a scanning signal generation section which is capable of generating h (his an integer of 2 or more) types of scanning signals, which suppliesthe scanning signal to each of the h scanning electrodes at the sametime in one period, and which supplies the scanning signal to each ofthe h scanning electrodes at the same time in another period;

a data signal supply section for supplying a data signal to each of thesignal electrodes;

a signal selection section for selectively controlling each of thescanning electrodes so as to be capable of producing a display or so asto be incapable of producing a display; and

a control section for controlling the scanning signal generation sectionin such a way that the scanning signal generation section supplies thescanning signal to the scanning electrode which is controlled by thesignal selection section so as to be capable of producing a display.

The signal selection section may comprise plural registers for storingdata for causing each of the scanning electrodes to be capable ofproducing a display or to be incapable of producing a display.

A scroll control section for controlling the signal selection sectionmay be provided so that the electrode which is capable of producing adisplay and the electrode which is incapable of producing a display aremade to shift as time elapses.

According to one aspect of the present invention, the method of drivinga liquid-crystal display device comprising a liquid-crystal displaypanel having a substrate having plural scanning electrodes in the formof lines, a substrate having plural signal electrodes in the form oflines, and a liquid-crystal layer interposed between the substrates, themethod comprising the steps of:

generating h (h is an integer of 2 or more) types of scanning signals,supplying the scanning signal to each of the h scanning electrodes atthe same time in one period, and supplying the scanning signal to eachof the h scanning electrodes at the same time in another period;supplying a data signal to each of the signal electrodes;

selectively controlling each of the scanning electrodes so as to becapable of producing a display or so as to be incapable of producing adisplay; and

controlling the scanning signal generation section in such a way thatthe scanning signal generation section supplies the scanning signal tothe scanning electrode which is controlled by the signal selectionsection so as to be capable of producing a display.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the entire construction of aliquid-crystal display device according to an embodiment of the presentinvention.

FIG. 1A is a plan view showing a liquid-crystal display panel of theliquid-crystal display device of FIG. 1.

FIG. 1B is a side view of the liquid-crystal display panel of FIG. 1A.

FIG. 2 is a block diagram showing details of a driving circuit on thescanning side and a signal selection circuit in FIG. 1.

FIG. 3 is a diagram showing waveforms of scanning signals supplied toscanning electrodes when the liquid-crystal display panel in FIG. 1 isdriven for the entire screen.

FIG. 4 is a front view showing the screen of the liquid-crystal displaypanel in FIG. 1, in which entire screen driving is being performed.

FIG. 5 is a diagram showing waveforms of scanning signals supplied toscanning electrodes when the liquid-crystal display panel in FIG. 1 isdriven partially.

FIG. 6 is a front view showing the screen of the liquid-crystal displaypanel, in which partial driving is being performed.

FIG. 7 is a table for illustrating various display modes which can berealized by the liquid-crystal display device.

FIG. 8A is a diagram showing waveforms of scanning signals supplied toscanning electrodes when the liquid-crystal display panel in FIG. 1 isdriven for the entire screen.

FIG. 8B is a diagram showing waveforms of scanning signals supplied toscanning electrodes when the liquid-crystal display panel in FIG. 1 isdriven partially.

FIG. 9 is a table for illustrating an example of a screen scrollingpattern for causing the liquid-crystal display panel in FIG. 1 to bepartially driven and to perform screen scrolling.

FIG. 10 is a table for illustrating another example of a screenscrolling pattern for causing the liquid-crystal display panel in FIG. 1to be partially driven and to perform screen scrolling.

FIG. 11 is a block diagram showing the entire construction of aliquid-crystal display device according to the conventional art.

FIG. 12 is a plan view showing a liquid-crystal display panel of theliquid-crystal display device in FIG. 11.

FIG. 13 is a diagram showing waveforms of scanning signals and datasignals applied to the liquid-crystal display panel in FIG. 11.

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of the present invention will be described below withreference to FIGS. 1 to 10. In this embodiment, an MLS driving method of4-line simultaneous driving in which four scanning electrodes are drivensimultaneously is adopted, but it is not intended that the presentinvention be limited to this embodiment.

As shown in FIG. 1, a liquid-crystal display device 1 according to theembodiment of the present invention comprises a liquid-crystal displaypanel 2, a liquid-crystal driving circuit 3, a liquid-crystal drivingvoltage generation circuit 4, and a driving control circuit 5. As shownin FIG. 1A, the liquid-crystal display panel 2 has plural scanningelectrodes (common electrodes) Y (Y1, Y2, . . . Ym) in the form oflines, and plural signal electrodes (segment electrodes) X (X1, X2, . .. Xn) in the form of lines intersecting at right angles to thesescanning electrodes in plan view. As shown in FIG. 1B, theliquid-crystal display panel 2 has a transparent or translucentsubstrate 10 on which the scanning electrodes Y are formed, atransparent or translucent substrate 11 on which the signal electrodes Xare formed, and a liquid-crystal layer 12 interposed between the twosubstrates 10 and 11.

For example, the number m of scanning electrodes is 64, and the number nof signal electrodes is 96. In order to drive the liquid-crystal displaypanel 2, the liquid-crystal driving circuit 3 supplies, to each scanningelectrode Y, a scanning signal which can differ according to each of thescanning electrodes and supplies, to each signal electrode X, a datasignal which can differ according to each of the signal electrodes. Theliquid-crystal driving voltage generation circuit 4, which is connectedto an input end of the liquid-crystal driving circuit 3, generates aliquid-crystal driving voltage. The driving control circuit 5 isconnected to the input ends of the liquid-crystal driving circuit 3 andthe liquid-crystal driving voltage generation circuit 4. When thedriving control circuit 5 receives display data and control data, thedriving control circuit 5 generates a display signal and supplies it tothe liquid-crystal driving circuit 3 and the liquid-crystal drivingvoltage generation circuit 4.

The liquid-crystal driving circuit 3 comprises a driving circuit 6 onthe scanning side as a scanning signal generation circuit connected toall the scanning electrodes Y1, Y2, . . . Ym of the liquid-crystaldisplay panel 2, and a driving circuit 7 on the signal side as a datasignal generation circuit connected to all the signal electrodes XI, X2,. . . Xn. The scanning electrodes Y are grouped in advance so that fouradjacent scanning electrodes belong to the same group. The drivingcircuit 6 on the scanning side drives four scanning electrodes Ybelonging to the same group. That is, the driving circuit 6 on thescanning side generates a scanning signal corresponding to each of thefour scanning electrodes Y in a predetermined selection period t1. Onthe other hand, the driving circuit 7 on the signal side generates adata signal corresponding to each one of the signal electrodes X1, X2, .. . Xn.

A signal selection circuit 8 for regulating an output of a scanningsignal from the driving circuit 6 on the scanning side to the scanningelectrodes Y is connected to the driving circuit 6 on the scanning side.The signal selection circuit 8 functions as a signal selection circuitfor selecting which scanning signal should be effectively supplied to acorresponding scanning electrode Y. In FIG. 1, the signal selectioncircuit 8 is shown as being separate and independent of the drivingcircuit 6 on the scanning side, but the driving circuit 6 on thescanning side may instead contain the signal selection circuit 8. Forexample, if the signal selection circuit 8 is housed, within one device,together with the driving circuit 6 on the scanning side and the drivingcircuit 7 on the signal side, the size of the liquid-crystal displaydevice 1 can be reduced.

As shown in FIG. 2, in this embodiment, the driving circuit 6 on thescanning side comprises 16 circuit sections 26 (26A, 26B, . . . 26P).These circuit sections 26A, 26B, . . . 26P correspond to 16 groups ofthe scanning electrodes, respectively, and four scanning electrodes Ybelong to each group. That is, scanning electrodes Y1 to Y4 of theliquid-crystal display panel 2 are connected to an output end of thecircuit section 26A, and scanning electrodes Y5 to Y8 thereof areconnected to an output end of the circuit section 26B. In a similarmanner, scanning electrodes Y61 to Y64 thereof are connected to thecircuit section 26P.

The signal selection circuit 8 comprises 64 registers REG1 to REG64corresponding to all the scanning electrodes Y1, Y2, . . . Ym,respectively. The content of each of the registers REG1 to REG64 is setto “1” or “0” based on the control of the driving control circuit 5, andeach of the registers REG1 to REG64 regulates the output of the scanningelectrode to a corresponding circuit section 26 according to thesetting. That is, in a case where a command signal indicating “1” isinput to one of the registers REG1 to REG64, that register REG outputs ascanning signal to a corresponding scanning electrode Y so that thisscanning electrode Y contributes to the display of the liquid-crystaldisplay panel 2. Scanning electrodes which can contribute to suchdisplay of the liquid-crystal display panel 2 are hereinafter called“display electrodes”. On the other hand, in a case where a commandsignal indicating “0” is input thereto, the register REG causes ascanning signal to a corresponding scanning electrode Y to be at a zeropotential (substantially stopping output of the scanning signal) so thatthis scanning electrode Y does not contribute to the display of theliquid-crystal display panel 2. Electrodes which do not contribute tosuch display thereof are hereinafter called “non-display electrodes”.

As a result of grouping the scanning electrodes Y1, Y2, . . . Ym of theliquid-crystal display device 1 into display electrodes and non-displayelectrodes under the control of the signal selection circuit 8 havingthe registers REG1 to REG64, display areas and non-display areas existin the liquid-crystal display device 1 according to this embodiment.This state is called “partial driving”. In this embodiment, it ispossible to group Y1, Y2, . . . Ym into display electrodes andnon-display electrodes irrespective of the grouping of the scanningelectrodes.

FIG. 6 shows the screen of the liquid-crystal display panel 2 in whichpartial driving is being performed. In FIG. 6, the diagonal shadingindicates non-display areas. On the other hand, FIG. 4 shows the screenof the liquid-crystal display panel 2 in which entire screen driving isbeing performed.

The driving control circuit 5 determines whether entire screen drivingshould be performed or partial driving should be performed on theliquid-crystal display panel 2 on the basis of control data. Whenpartial driving should be performed, the driving control circuit 5further determines which scanning electrodes Y should be set as displayelectrodes. Based on the determination, the driving control circuit 5supplies each command signal indicating “1” or “0” to the registers REG1to REG64 of the signal selection circuit 8. Whereas in the entire screendriving, a command signal indicating “1” is supplied to all theregisters REG1 to REG64, in the partial driving, a command signalindicating “1” is supplied to registers corresponding to the displayelectrodes and a command signal indicating “0” is supplied to theregisters corresponding to the non-display electrodes.

FIG. 3 shows examples of outputs of scanning signals in a case where allthe scanning electrodes Y1, Y2, . . . Ym are set to be displayelectrodes (in the case of the entire screen driving). In FIG. 3,references n to n+3 are numbers which are given to scanning electrodes Ywhich contribute to display. In the case of entire screen driving, therelationships between the scanning electrodes Y1, Y2, . . . Ym and linesn to n+3 are as shown in Table 1.

TABLE 1 Line n Scanning electrodes Y1, Y5, Y9, . . . Y61 (Suffix is anumber with a remainder of 1 when divided by 4) Line n + 1 Scanningelectrodes Y2, Y6, Y10, . . . Y62 (Suffix is a number with a remainderof 2 when divided by 4) Line n + 2 Scanning electrodes Y3, Y7, Y11, . .. Y63 (Suffix is a number with a remainder of 3 when divided by 4) Linen + 3 Scanning electrodes Y4, Y8, Y12, . . . Y64 (Suffix is a numberwhich is divisible by 4)

As shown in FIG. 3, four scanning electrode lines n to n+3 belonging toone group are simultaneously driven in four selection periods t1 in oneframe. However, the voltage levels output by the lines n to n+3 in eachselection period t1 differ from one another. Since the voltage level ofthe scanning signal exists at two levels, +V2 and −V2, in thisembodiment in which four scanning electrode lines are drivensimultaneously, the number of pulse patterns which can be realized byone group in one selection period t1 is 2⁴=16. In order to control thevoltage levels of the lines n to n+3 according to each selection periodt1 in this manner, signals FR1 and FR2 are supplied from the drivingcontrol circuit 5 shown in FIG. 1 to the circuit sections 26A to 26P ofthe driving circuit 6 on the scanning side. In the selection period t1,each of the circuit sections 26A to 26P controls, based on the signalsFR1 and FR2, the voltage levels to be output to the lines n to n+3, forexample, in accordance with the rules in Table 2. Table 2 shows therelationships between the values of the signals FR1 and FR2 and thevoltage levels output from the lines n to n+3.

TABLE 2 Signal FR1 1 0 1 0 Signal FR2 1 1 0 0 Line n V2 V2 −V2   V2 Linen + 1 −V2   V2 V2 V2 Line n + 2 V2 −V2   V2 V2 Line n + 3 V2 V2 V2 −V2  

As shown in Table 2 and in FIG. 3, in the first selection period t1 inone frame, the signals FR1 and FR2 are at a high level (1), and whereasa voltage V2 is supplied to the lines n, n+2, and n+3, a voltage −V2 issupplied to the line n+1. In the next selection period t1, the signalFR1 is at a high level, but the signal FR2 is at a low level (0), andwhereas a voltage V2 is supplied to the lines n, n+1, and n+3, a voltage−V2 is supplied to the line n+2. That is, the voltage level state ofeach line, given in one selection period t1, differs from the voltagelevel state in another selection period t1.

TABLE 3 Command Signal Registers signals electrodes X Circuit section26A REG1 0 — REG2 0 — REG3 1 Line n REG4 1 Line n + 1 Circuit section26B REG5 1 Line n + 2 REG6 1 Line n + 3 REG7 0 — REG8 0 — Circuitsection 26C REG9 0 — REG10 1 Line n REG11 0 — REG12 1 Line n + 1 Circuitsection 26D REG13 1 Line n + 2 REG14 1 Line n + 3 REG15 0 — REG16 1 Linen Circuit section 26E REG17 1 — . . . . . . . . . . . .

Next, partial driving is described in which some electrodes are set asnon-display electrodes as a result of setting each command signal to theregisters REG1 to REG64. In this embodiment, since it is possible togroup Y1, Y2, . . . Ym into display electrodes and non-displayelectrodes irrespective of the grouping of the scanning electrodes, therelative relationships between the scanning electrodes Y1, Y2, . . . Ymin the partial driving and the lines n to n+3 differ from theabove-described relative relationships in the entire screen driving. Forexample, in a case where command signal groups such as those shown inTable 3 are input to the registers REG1 to REG64, the third scanningelectrode Y3 is at line n, and the fourth scanning electrode Y4 is atline n+1.

As described above, in this embodiment, in the partial driving, which ofthe scanning electrodes Y1, Y2, . . . Ym the lines n to n+3 correspondto, respectively, is not determined in advance. This relativerelationship is determined by the driving control circuit 5 (refer toFIG. 1). After the driving control circuit 5 determines which scanningelectrodes Y should be set as display electrodes, the driving controlcircuit 5 supplies signals A1 and A2 as line information to all thecircuit sections 26A to 26P. Each of the signals A1 and A2 indicates “0”or “1”, and a pair of signals A1 and A2 represent 2-bit information. Allthe display electrodes are assigned a pair of signals A1 and A2, andeach combination of the signals A1 and A2 represents one of the lines nto n+3, as shown in Table 4.

TABLE 4 Signal A1 Signal A2 Line n 0 0 Line n + 1 0 1 Line n + 2 1 0Line n + 3 1 1

Therefore, the circuit sections 26A to 26P receive line informationindicating which scanning electrode Y corresponds to the lines n to n+3.Based on the signals A1 and A2 which are line information and theabove-described signals FR1 and FR2, each of the circuit sections 26A to26P controls the voltage level to be output to the display electrodes(lines n to n+3) in the selection period t1.

Specifically, in the case of the entire screen driving, as shown inTable 1, since all the scanning electrodes Y1, Y2, . . . Ym are assignedto one of the lines n to n+3, respectively, the driving control circuit5 supplies line information corresponding to all the scanning electrodesY1, Y2, . . . Ym to the circuit sections 26A to 26P. Then, as describedabove, based on the line information and the signals FR1 and FR2, in theselection period t1, each of the circuit sections 26A to 26P controlsthe voltage level to be output to all the scanning electrodes Y1, Y2, .. . Ym (lines n to n+3), for example, in accordance with the rules inTable 2.

On the other hand, in the case of the partial driving, based on the lineinformation and the signals FR1 and FR2, in the selection period t1,each of the circuit sections 26A to 26P controls the voltage level to beoutput to some of the display electrodes (lines n to n+3). However, alsoin the partial driving, control of the voltage level can be performed inaccordance with rules similar to that for the entire screen driving, forexample, the rules shown in Table 2. FIG. 5 shows examples of outputs ofscanning signals in a case where some of the scanning electrodes Y areset as display electrodes (in the case of the partial driving). Sincethe lines n to n+3 are driven in accordance with the same rules shown inTable 2, the sequence of the rise and fall of the voltage is the same inFIGS. 3 and 5.

However, in the partial driving, since only some of the scanningelectrodes Y1, Y2, . . . Ym are driven, the driving frequency of thedisplay electrodes can be decreased in comparison with that for theentire screen driving, making it possible to reduce power consumption.This will next be described specifically.

For example, in this embodiment, the frame frequency is fixed to 40 Hz,that is, the period of one frame is fixed to 25 milliseconds. Herein, aframe is the period required to scan one display area of theliquid-crystal display panel 2 once, that is, the period required todrive all the display electrodes once. In this embodiment, since fourscanning electrodes Y are driven at one time, in order that 64electrodes Y be driven four times (there are four selection periods t1in one frame) due to the entire screen driving, the duty cycle becomes{fraction (1/64)}, and the span of one selection period t1 becomes{fraction (25/64)}=0.39 milliseconds.

On the other hand, for example, suppose partial driving in which 16electrodes Y are assigned as display electrodes. In this embodiment,since four scanning electrodes Y are driven at one time, in order todrive 16 display electrodes four times, the duty cycle becomes {fraction(1/16)}, and the span of one selection period t1 becomes {fraction(25/16)}=1.56 milliseconds. In this manner, the frequency of voltagechanges can be reduced. The change of the duty cycle that determines thespan of the selection period t1 can be performed by the calculation bythe driving control circuit 5, for example, on the basis of display dataand control data.

Referring to FIG. 7, various modes of displays according to thisembodiment will now be described. The column (a) of FIG. 7 shows a casein which 8 lines are displayed by being divided into two rows.Specifically, as a result of a command signal indicating “1” being inputto registers REG3 to REG6 and registers REG11 to REG14, scanningelectrodes Y3 to Y6 and scanning electrodes Y11 to Y14 are set asdisplay electrodes. The scanning electrodes Y3 to Y6 are driven in sucha manner as to correspond to the lines n to n+3, respectively, and thescanning electrodes Y11 to Y14 are driven in such a manner as tocorrespond to the lines n to n+3, respectively. In this embodiment,since four scanning electrodes Y are driven at one time, in order todrive eight display electrodes four times, the duty cycle becomes ⅛.Although FIG. 7 shows only the registers REG1 to REG16 for the sake ofsimplicity, a larger number of registers may be provided in practice.

The column (b) of FIG. 7 shows a case in which 16 lines are shownwithout being divided. The duty cycle in this case is {fraction (1/16)}.

The column (c) of FIG. 7 shows a case in which eight lines are displayedin one row without being divided. Specifically, as a result of a commandsignal indicating “1” being input to registers REG5 to REG12, continuousscanning electrodes Y5 to Y12 are set as display electrodes. Thescanning electrodes Y5 to Y8 are driven in such a manner as tocorrespond to the lines n to n+3, respectively, and the scanningelectrodes Y9 to Y12 are driven in such a manner as to correspond to thelines n to n+3, respectively. Also in this case, the duty cycle becomes⅛.

A description is given again of a scanning signal output to a scanningelectrode Y when a command signal indicating “1” or “0” is input to eachregister REG. As shown in FIG. 8A, when a command signal indicating “1”is input to all the registers REG1 to REG4, the scanning electrodes Y1to Y4 are driven simultaneously. On the other hand, as shown in FIG. 8B,in a case where “0” is written into the registers REG1 and REG2 and “1”is written into the registers REG3 and REG4, the signals correspondingto the registers REG1 and REG2 reach a zero potential, an output of asignal to the scanning electrodes Y1 and Y2 is stopped substantially,and only the scanning electrodes Y3 and Y4 corresponding to theregisters REG3 and REG4 are driven. At this time, the scanningelectrodes Y3 and Y4 corresponding to the registers REG3 and REG4 intowhich “1” is written are assigned lines n, n+1, . . . in sequence fromthe top side. Although FIG. 8 shows only the registers REG1 to REG4 forthe sake of simplicity, a larger number of registers is provided inpractice.

As is clear from the foregoing description, in the liquid-crystaldisplay device 1 according to this embodiment, since the signalselection circuit 8 comprising plural registers REG1 to REG64 forregulating an output of a scanning signal is provided in the drivingcircuit 6 on the scanning side, it is possible to diversify displays onthe screen of the liquid-crystal display panel 2 irrespective of thegrouping of the scanning electrodes Y. Specifically, as is clear fromTable 3 and FIG. 7, the widths of display areas and non-display areascan be changed as desired without being limited to the number ofscanning electrodes Y which are driven simultaneously. That is, thewidths of display areas and non-display areas can be selectedindependently of the multiple of the number of scanning electrodes Ywhich are driven simultaneously. Furthermore, a variety of multi-rowdisplays such as those shown in FIGS. 6 and 7 are possible.

In addition, in this embodiment, by supplying line information to thecircuit sections 26A to 26P, also in the partial driving, the voltagelevel can be controlled in accordance with the same rules (refer to FIG.2) as those in the case of the entire screen driving. Furthermore, whenthe command signal which is input to the registers REG1 to REG64 is “0”,since the scanning signal is not output to the scanning electrodes Y,power consumption of the non-display areas can be reduced.

In this embodiment, furthermore, as described below, the screenscrolling of the liquid-crystal display panel 2 can also be performed.

FIG. 9 shows an example of a screen scrolling pattern which can berealized by the liquid-crystal display device 1 according to thisembodiment. This scrolling pattern is used in partial driving in whichdisplay areas in two rows are provided. That is, on the screen of theliquid-crystal display panel 2, whereas a display area which is realizedby eight scanning electrodes Y is provided in the upper row, also in thelower row, a display area which is realized by 8 scanning electrodes Yas in the upper row is provided.

Specifically, in a first step, whereas the contents of the registersREG1 to REG8 and the registers REG17 to REG24 are set to “1”, thecontents of the other registers REG are maintained at “0”. As a result,the scanning electrodes Y1 to Y8 and the scanning electrodes Y17 to Y24become display electrodes, and display areas in two rows are provided.

In the next step, the contents of only the registers REG2 to REG9 andthe registers REG18 to REG25 are set to “1”. As a result, the registersREG2 to REG9 and the registers REG18 to REG25 become display electrodes,and display areas of the two rows are moved downward together.Hereafter, regarding the display area at the upper row, the registersREG into which the content “1” is input are changed regularly, such asthe registers REG3 to REG10 being set to “1” and then the registers REG4to REG11 being set to “1”. Also regarding the display area at the lowerrow, the registers REG into which the content “1” is input are changedregularly, such as the registers REG19 to REG26 being set to “1” andthen the registers REG20 to REG27 being set to “1”. In this manner, thedisplay areas in two rows move downward regularly and synchronously.

In order to realize screen scrolling, the driving control circuit 5supplies a command signal periodically to registers REG in order toupdate the contents thereof. Each time such a command signal is suppliedto the registers REG, the driving control circuit 5 supplies the signalsA1 and A2 as line information indicating which scanning electrode Ycorresponds to the lines n to n+3 to all the circuit sections 26A to26P, so that the relative relationships between each scanning electrodeY and the lines n to n+3 are updated. Although FIG. 9 shows only theregisters REG1 to REG32 for the sake of simplicity, a larger number ofregisters may be provided in practice.

FIG. 10 shows another example of a screen scrolling pattern which can berealized by the liquid-crystal display device 1 according to thisembodiment. In this scrolling pattern, regarding the display area at thelower row, the registers REG into which “1” is input are changedregularly, such as at the first step, the contents of the registersREG17 to REG24 being set to “1”, at the next step, the contents of theregisters REG18 to REG25 being set to “1”, furthermore, the registersREG19 to REG26 being set to “1”, and next, the registers REG20 to REG27being set to “1”. However, regarding the display area at the upper row,from the first step, the contents of the registers REG1 to REG8 aremaintained at “1”. Therefore, while the display area at the upper row isfixed, only the display area at the lower row is scrolled. As describedabove, according to this embodiment, screen scrolling can also berealized easily, and furthermore, a variety of scrolling modes can beachieved.

In addition, by alternately writing the content “1” and “0” into eachregister and by appropriately changing the duty cycle for setting theselection period t1, it is also possible to cause the display in eachline to blink.

The embodiment of the present invention has thus been described. Theprinciples used in this embodiment can also be applied to theliquid-crystal display device 100 according to the conventional artdescribed with reference to FIGS. 11 to 13. As a result, also in theliquid-crystal display device 100, display areas and non-display areascan be set and screen scrolling can be realized irrespective of thegrouping of the scanning electrodes Y. Modifications of such aliquid-crystal display device 1 are within the scope of the presentinvention.

What is claimed is:
 1. A liquid crystal display device, comprising: aliquid crystal display panel including a first substrate having aplurality of groups of scanning electrodes, each group containing atleast two scanning electrodes, a second substrate having a plurality ofsignal electrodes, and a liquid-crystal layer interposed between thefirst and second substrates; a control circuit that outputs commandsignals comprising a plurality of commands, one for each scanningelectrode, indicative of which scanning electrodes are to be activated,outputs line information signals that respectively assign each of theto-be-activated scanning electrodes to a particular one of a pluralityof scanning electrode lines, and outputs pulse control signalsindicative of pulses to be applied to the scanning electrode linesduring a particular time period; a scanning signal circuit that outputsa first group of scanning signals at substantially the same time duringone time period to a first set of scanning electrodes, each of which isassigned to a different one of the scanning electrode lines, and outputsa second group of scanning signals at substantially the same time duringanother time period to a second set of scanning electrodes, each ofwhich is assigned to a different one of the scanning electrode lines, inresponse to the command, line information and pulse control signalsoutput by the control circuit; a data signal circuit that outputs datasignals to the signal electrodes; a signal selection circuit having aplurality of registers, one for each scanning electrode, wherein eachregister receives and stores a corresponding command indicating whetheror not the corresponding scanning electrode is to be activated; and ascroll circuit that controls the setting of the commands stored in theregisters so that the scanning electrodes are selectively activated astime elapses to generated a screen scrolling pattern; wherein thescanning electrodes are selectively controlled and activated to generateone of plurality of display patterns during a particular time periodirrespective of the grouping of the scanning electrodes.
 2. A liquidcrystal display device, comprising: a liquid crystal display panelincluding a first substrate having a plurality of groups of scanningelectrodes, each group containing at least two scanning electrodes, asecond substrate having a plurality of signal electrodes, and aliquid-crystal layer interposed between the first and second substrates;a control circuit that outputs command signals comprising a plurality ofcommands, one for each scanning electrode, indicative of which scanningelectrodes are to be activated, outputs line information signals thatrespectively assign each of the to-be-activated scanning electrodes to aparticular one of a plurality of scanning electrode lines, and outputspulse control signals indicative of pulses to be applied to the scanningelectrode lines during a particular time period; a scanning signalcircuit that outputs a first group of scanning signals at substantiallythe same time during one time period to a first set of scanningelectrodes, each of which is assigned to a different one of the scanningelectrode lines, and outputs a second group of scanning signals atsubstantially the same time during another time period to a second setof scanning electrodes, each of which is assigned to a different one ofthe scanning electrode lines, in response to the command, lineinformation and pulse control signals output by the control circuit; adata signal circuit that outputs data signals to the signal electrodes;and a signal selection circuit having a plurality of registers, one foreach scanning electrode, wherein each register receives and stores acorresponding command indicating whether or not the correspondingscanning electrode is to be activated; wherein the scanning electrodesare selectively controlled and activated to generate one of plurality ofdisplay patterns during a particular time period irrespective of thegrouping of the scanning electrodes; and wherein the scanning signalcircuit and the signal selection circuit are embodied as a singlecircuit.